Aromatic copolyestercarbonates have been known for many years. Their chief property improvement over polycarbonate is a higher distortion temperature under load, allowing it to be used in applications wherein higher temperature properties are required than standard polycarbonates. However, together with the higher temperature properties is the increased difficulty in molding. The melt viscosity is high, therefore requiring a higher temperature and/or more pressure to mold in comparison to the standard polycarbonates.
Various monofunctional groups have been employed to terminate polymers of the polycarbonate family. The standard endcapping monomers are pheno and paratertiary butylphenol. However, other endapping agents have been disclosed from time to time. In U.S. Pat. No. 3,697,481, Bialous, et al assigned to General Electric Company, a chromanyl radical has been employed to end-cap polycarbonates. The description of polycarbonates is broad enough to include copolyestercarbonates such as disclosed in U.S. Pat. Nos. 3,030,331 and 3,169,121, see the 3,697,481 U.S. Pat. No. at column 3, lines 59-69. In U.S. Pat. No. 4,238,596 issued to Quinn and assigned to General Electric Company, a new method for preparing copolyestercarbonates is disclosed. Following this new method, Examples 3 and 6 utilize chroman-I as a chain stopper. In Example 3, an aromatic copolyestercarbonate of 18 mole percent ester content in prepared utilizing 100 percent isophthalate units. In Example 6 an aromatic copolyestercarbonate is prepared having 11 percent ester content utilizing 100 percent terephthalate units. The data in the Tables in the U.S. Pat. No. 4,238,596 patent compares all of the examples. Reducing the ester content and going to chroman as the endcapping agent, see Examples 1-3, increases the Notched Izod. However, in Examples 4 and 6, which are 100 percent terephthalate content, the Notched Izod does not shift from Example 4 to Example 6. The only difference in the Examples is the chroman endcap compared with the phenol endcap. With respect to melt viscosity the melt index is somewhat higher in Example 3 than Examples 1 and 2 in the '596 patent wherein the ester content goes down but chroman replaces the phenol. In Examples 4 and 6 the melt index is lower in Example 6 than Example 4. In none of the Chroman endcapped examples is there a significant shift in distortion temperature under load to a higher value.
New aromatic copolyestercarbonates are being disclosed and patented. An example of such a copolyestercarbonate is found in U.S. Pat. No. 4,506,065 issued to Miller, et al and assigned to General Electric Company, wherein the specific content of the ester units and ester mole percent is emphasized. The standard methods for preparation is disclosed by reference to specific patents. These patents are U.S. Pat. Nos. 4,238,596, previously mentioned, and the U.S. Pat. No. 4,238,597 counterpart which were both incorporated into U.S. Pat. No. 4,506,065 by reference, see column 2, lines 58-61.
New chainstopped aromatic copolyestercarbonates have been discovered. These copolyestercarbonates end-capped with a member of the chromanyl family, preferably chromanyl-I, exhibit interesting processing and physical properties. These polymers can exhibit increased distortion temperature under load and improved impact resistance under normal conditions as well as under heat and aging conditions. Additionally, the lower viscosity chromanyl endcapped polymers show positive advantages in color retention and smaller loss in viscosity upon processing than the higher viscosity chromanyl endcapped polymers without sacrificing certain physical properties.